The applicant proposes a study aimed at delineating associations between executive processes, genes, and frontalstriatal brain structure in attention deficit hyperactivity disorder (ADHD). ADHD is associated with well- documented weaknesses in executive processing, including deficits in response inhibition (Rl) and working memory (WM). Evidence suggests that these deficits may be heritable and sensitive to genetic control. In addition, research has begun to characterize the specific neural substrates that mediate these executive processes. Given promising evidence for mediation of Rl and WM through genetic influences and neural pathways, these executive processes may be useful intermediate phenotypes for determining genetic and neural etiologies of ADHD. The proposed study involves collecting neuropsychological data in the domains of Rl and WM, genetic material, and anatomical brain images (as part of an ongoing functional magnetic resonance imaging study) from adults with ADHD and control participants. Specific associations between task performance, genotypes, volumes of putatively involved brain regions, and ADHD symptoms will be investigated. Findings will characterize the contributions of genetic variations and neural structures on executive processing in ADHD, as well as identify potentially useful genetic and neural intermediate phenotypes for future genetic studies of ADHD. [unreadable] [unreadable] [unreadable]